In the search for energy saving, a trend in public lighting and more generally to area lighting, is to use intelligent lighting system, i.e. system which dims down the light when nobody is in the area and to switch automatically to full power when a pedestrian is approaching. The man skilled in the art understands that an intelligent lighting system saves cost and energy, especially for municipalities, by lighting the area only when necessary.
A classical intelligent lighting system comprises a network of luminaires, a system of presence detectors for detecting anyone (car, pedestrian, biker, etc) in the street, and a central electronic unit for controlling/coordinating the power supply of the luminaires according to the events detected by the detectors.
The communication between the central electronic unit and the luminaires may use a wireless communication network in which each luminaire is a node of the network. Therefore, the spatial structures of the lighting array and communication network are equivalent.
After an installation of an intelligent lighting system, it is necessary to commission each luminaire. Classically, it is a manual step in which each luminaire is identified in the network and for the control unit and an addressing address is assigned to it.
Thus, after commissioning, there is a perfect isomorphism between the wireless network and the lighting array, each luminaire having its known wireless node and reciprocally.
However, a significant disadvantage is that the commissioning process is time consuming for the installer. For instance, the commissioning electrician must selectively actuate luminaires or groups of luminaires and allocate them some addresses.
To overcome the disadvantage of a manual commissioning process, it has been proposed to use Received Signal Strength Indication (RSSI) or Time-of-Flight techniques to discover the wireless network spatial topography and, knowing the spatial topography of luminaires, to map the wireless network onto the luminaire network.
For instance, patent application WO 01/97 466 discloses a method to determine a wireless network configuration by using a range between stations computed from the signal strength of the transceivers involved in the connection and a central controlling unit to control nodes in the network, method which may be used for an automatic commissioning process.
However, these types of range measurement might be subject to error and, hence, the derived position of the communication nodes often do not match exactly to positions on the grid or lattice arrangement on which the luminaire are arranged. There is, therefore, uncertainties as to which luminaire each node is associated with.
Therefore, complex computing algorithms are used to correct the errors.
Consequently, the discovering method of the wireless network spatial topography and the error correction to map it onto the luminaires network requires some intensive computing process and is not error-prone.